(Editor’s Note: These excerpts are from the book Idaho Chronology, Nomenclature and Bibliography by John E. Rees, published in 1918. In the Nomenclature section, Rees offers his best information and beliefs regarding the origins, meanings and history behind Idaho place names and prominent figures. Born in 1868, Rees grew up in Lemhi County, taught literature and history in Salmon City for 15 years where he served as a prosecuting attorney the same year this book was published. He died in 1928 of heart failure.)
ADA. –Named for Ada Riggs, the oldest daughter of Hon. H. C. Riggs, and who was the first white child born in Boise City, in 1863. The county seat is Boise, named for the Boise River.
ADAMS. –Names for John Adams, who was President of the United States from 1797-1801, being second to General Washington, and this county was created from Washington County. The county seat is Council.
BANNOCK. –Named for the Bannack Indians, but the Scotch word is used. The county seat is Pocatello, named for Chief Pokatello.
BEAR LAKE. –Named for Bear Lake, which is within its borders. The county seat is Paris, named by recent Mormon converts from France who settled there in 1863.
BENEWAH. –Named for an old chief of the Coeur d’Alene Indians who was an historic and notorious individual of that locality. The county seat is St. Maries, named by Father De Smet in 1842.
BINGHAM. –Named by Governor Bunn for his friend Congressman Henry H. Bingham of Philadelphia Pa. The county seat is Blackfoot, named for the Blackfoot Indians.
BLAINE. –Named for Hon. James G. Blaine, the American statesman. The county seat is Hailey, named for Hon. John Hailey.
BOISE. –Named for the Boise River. The County seat is Idaho City.
BONNER. –Named for Bonners Ferry. The county seat is Sandpoint, named for a large sand bar that extends into Pend Oreille Lake at this place.
BONNEVILLE. –Named for Captain Bonneville. The County seat is Idaho Falls, named for some falls in Snake River nearby. This place was originally called Eagle Rock.
BOUNDARY. –Named from the fact that it joins the Canadian boundary. The county seat is Bonners Ferry.
BUTTE. –Named for the Buttes. The county seat is Arco, named by the first settlers for a small town in Tyrol, Austria.
CAMAS. –Named for Big Camas Prairie. The county seat is Fairfield, named by reclamation settlers as descriptive of the country.
CANYON. –Named for the canyon on the Boise River near Caldwell. The county seat is Caldwell, named for Senator Alexander Caldwell of Kansas.
CASSIA. –Named for Cassia Creek, which was so called by the Hudson Bay trappers, who found some cassia plant on the stream. The county seat is Albion, named by Mr. Robinson, one of the promoters of the town, which was founded in 1875.
CLEARWATER. –Named for the Clearwater River. The county seat is Orofino.
CUSTER. –Named for Gen. George A. Custer, who was killed at the battle of Little Bighorn on June 25, 1876. The county seat is Challis, named for A. P. Challis, who, in 1878, founded the town.
ELMORE. –Named for the Ida Elmore, a famous quartz mine, discovered in 1863. The county seat is Mountain Home.
FRANKLIN. –Named from the town of Franklin. The county seat is Franklin, named for Mr. Franklin, the leader of the thirteen Mormon families that settled the place in 1860.
FREMONT. –Named for General John C. Fremont, who traversed Idaho in 1843. The county seat is St. Anthony, named by C. H. Moon, who in 1887 build a bridge and store there and called it thus because of its fancied resemblance to St. Anthony Falls, Minnesota.
GEM. –Named for “Gem of the Mountains.” The county seat is Emmett, named for Emmett Cahalan, the first white boy born there and who was the oldest son of T. D. Cahalan, an early settler and attorney.
GOODING. –Named for Governor Frank R. Gooding. The county seat is Gooding, named for the same party.
IDAHO. –Named for a steamboat that flied the Columbia River from and after 1860. The county seat is Grangeville, named by L. P. Brown, the found of the town, for the grange organization.
JEFFERSON. –Named for President Jefferson. The county seat is Rigby, named for William F. Rigby, a local authority of the Mormon Church, and one of the founders of the town.
KOOTENAI. –Named for Kutenai Indians. The county seat is Coeur d’Alene, named for the Coeur d’Alene Indians.
LATAH. –Named for the Nez Perce Indian word Latah. The county seat is Moscow, so named when the post office was moved, during the ‘70s, one mile west of the old site by a Russian by the name of Hogg.
LEMHI. –Named for Fort Lemhi. The county seat is Salmon, named for the Salmon River.
LEWIS. –Named for Capt. Meriwether Lewis of the Lewis and Clark expedition, 1804-06. The county seat is Nez Perce, named for the Nez Perce Indians.
LINCOLN. –Named for President Lincoln. The county seat is Shoshone, named for the Shoshoni Indians.
MADISON. –Named for President Madison. The county seat is Rexburg, named for Thomas Ricks, a local authority of the Mormon Church, and is a corruption of Ricksburg.
MINIDOKA. –This is a Shoshoni word meaning “broad expanse,” and is applied to this place because it is near the broadest portion of the Snake River plains. The county seat is Rupert, named for a reclamation expert.
NEZ PERCE. –Named for the Nez Perce Indians. The county seat is Lewiston, named for Capt. Meriwether Lewis of the Lewis and Clark expedition 1804-6.
ONEIDA. –Named for Oneida, New York, from which place most of the early settlers had come. The county seat is Malad, named for the Malade River.
OWYHEE. –Named for the Owyhee River. The county seat is Silver City, named, in 1863, by the prospectors who discovered rich silver float near there.
PAYETTE. –Named for the Payette River. The county seat is Payette, named for the same.
POWER. –At American Falls the Snake River is one thousand feet wide and drops forty-two feet over a series of beautiful cascades, making it possible to develop several thousand horsepower. This county includes this power site, and from it derives its name. The county seat is American Falls.
SELWAY. –This is a Nez Perce Indian word meaning the “stream of easy canoeing.” The county seat is Kooskia, an adaptation of the two syllables taken from the word Koos-koos-kia.
SHOSHONE. –Named for the Shoshoni Indians. The county seat is Wallace, named for Col. W. R. Wallace, the locator of the townsite.
TETON. –Named for the Teton peaks. The county seat is Driggs, named, in 1888, for A. P. Driggs, a local authority of the Mormon church.
TWIN FALLS. –Named for the Little or Twin Falls of the Snake River. The county seat is Twin Falls, named for the same.
VALLEY. –Named for Long Valley which lies within its borders. The county seat is Cascade, named for the Cascade Falls on the Payette River which are nearby.
WASHINGTON. –Named for the “Father of our Country.” The county seat is Weiser, named for the Weiser River.
(Editor’s Note: Counties were still being added, combined or removed during the period Idaho Nomenclature was published. Today, there are 44 counties in Idaho; Rees listed one, Selway which I can’t find a reference for and seems to be part of Idaho County because he said the county seat was Kooskia. In 1919, two counties were added, after Rees made his list: Caribou and Clark. Here’s a map of current Idaho counties, which is also a guide to Idaho license plates. From Wikipedia’s entry List of Counties in Idaho: “Since 1945, each county has used a code on its license plates that features the first letter of the county’s name. Where the names of two or more counties start with the same letter, in each of these counties the letter is preceded by a number indicating that county’s order in the alphabetical list. For instance, the four counties beginning with ‘L’ in alphabetical order are Latah, Lemhi, Lewis and Lincoln; the codes for these counties are thus 1L, 2L, 3L and 4L respectively. Elmore, Idaho, Kootenai, Nez Perce, Shoshone, Valley, and Washington Counties are the only ones in the state with their respective first letters; in these counties, the letter alone serves as the code.”)